ELECTRONIC STRUCTURE OF TIO2 THIN FILMS AND LAALO3-SRTIO3 HETEROSTRUCTURES: THE ROLE OF TITANIUM 3D1 STATES IN MAGNETIC AND TRANSPORT PROPERTIES

The scope of this Thesis is the study of the electronic structure of two Ti-based oxide systems, TiO2 thin films and the ultra-thin LaAlO3-SrTiO3 (LAO-STO) heterojunctions, which display remarkable physical phenomena, so far not completely understood. In both cases, the titanium-related electronic states are expected to play a fundamental role and thus have been probed by means of X-ray photoemission spectroscopies. A weak room-temperature ferromagnetism (FM) has been recently detected in slightly reduced TiO2 thin film and in other oxides, such as HfO2 and CaO; since these materials are insulating closed-shell systems, this phenomenon has been classified as "d0 magnetism". Magnetism in these compounds seems to be related to the growth methodology and ultimately to the presence of structural defects, such as oxygen vacancies. Therefore, a thorough analysis of titanium electronic states, and especially of the defect-related Ti3+ energy levels, is needed in order to understand the origin of magnetic interactions. In the first part of this Thesis, a comprehensive magnetic characterization of a set of TiO2 samples is given, together with the analysis of Ti 3d-related states carried out with X-ray photoemission (XPS) and resonant photoemission (ResPES). A set of N-doped TiO2 thin films have also been grown, in order to verify the effect of doping on the TiO2 magnetism. The hypothesis of a clustered oxygen-vacancies origin of FM is then discussed in the light of the experimental and theoretical results. Another interesting oxide system in which the stoichiometry of Ti ions play a fundamental role is the LAO-STO interface. LAO and STO, separately, are two band insulators, with an empty shell electronic structure (3d0 for STO, 4f0 for LAO) and a similar perovskite structure; however, the interface created by growing LAO on the top of STO (001) has found to become metallic, hosting a 2D electron gas. This heterostructure becomes conductive only when the STO is terminated with a TiO2 layer; therefore, the Ti-related electronic states are expected to host the metallic states. The second part of this Thesis is devoted to the study of conductive and insulating LAO-STO interfaces, carried out by XPS, X-ray absorption (XAS) and with ResPES techniques. The stoichiometry of each atomic species has been evaluated through a comparison with LAO and STO single crystals. A resonance enhancement of the conductive Ti states, associated to a small fraction of Ti3+ ions is reported and compared to theoretical calculations. On the basis of these results, the origin of metallic states in ultra-thin LAO-STO interfaces is properly addressed. In addition, a characterization of the intermixing and the disorder at the LAO-STO interface has been done through angle-resolved XPS, providing important information on the intermixing of light cations (Al, Ti) otherwise missed by X-ray diffraction techniques

Ultrasound and MRI appearance of abnormally adherent placenta in a woman with Asherman's syndrome

: Although 10% of pregnancies following treatment of Asherman's syndrome are estimated to have abnormal placental adhesion, there is a paucity of reports describing imaging features in such cases. We describe ultrasound and MRI features in one of such cases, showing a peculiar pattern of shallow but diffuse abnormally adherent placenta

Acute hepatitis caused by minocycline.

n/

Environmental monitoring of low-ppb ammonia concentrations based on single-wall carbon nanotube chemiresistor gas sensors: Detection limits, response dynamics, and moisture effects

EUROSENSORS 2014, the XXVIII edition of the conference series.Under a Creative Commons license.We present single-wall carbon nanotube (SWCNT) chemiresistor gas sensor (CGS) operating at room temperature, displaying an enhanced sensitivity to NH3. Ammonia concentrations in the full range of the average [NH3] in a urban environment have been measured, and a detection limit of 3 ppb is demonstrated, which is well below the sensitivities so far reported for non- functionalized SWCNTs operating at room temperature. Different materials were tested as substrates, including cheap plastic flexible substrates. In addition to a careful preparation of the SWCNT layers, the low-ppb limit is also attained by revealing and properly tracking a fast dynamics during the desorption process. On the basis of these results a model of the CGS response vs time is proposed. When functionalized with indium-tin oxide nanoparticles, a sensitivity increase is detected, along with a remarkable selectivity towards moisture.Peer Reviewe

Deep neural network for x-ray photoelectron spectroscopy data analysis

In this work, we characterize the performance of a deep convolutional neural network designed to detect and quantify chemical elements in experimental x-ray photoelectron spectroscopy data. Given the lack of a reliable database in literature, in order to train the neural network we computed a large (<100 k) dataset of synthetic spectra, based on randomly generated materials covered with a layer of adventitious carbon. The trained net performs as well as standard methods on a test set of 48500 well characterized experimental x-ray photoelectron spectra. Fine details about the net layout, the choice of the loss function and the quality assessment strategies are presented and discussed. Given the synthetic nature of the training set, this approach could be applied to the automatization of any photoelectron spectroscopy system, without the need of experimental reference spectra and with a low computational effort

Loeys-Dietz syndrome type I and type II: clinical findings and novel mutations in two Italian patients

Loeys-Dietz syndrome (LDS) is a rare autosomal dominant disorder showing the involvement of cutaneous, cardiovascular, craniofacial, and skeletal systems. In particular, LDS patients show arterial tortuosity with widespread vascular aneurysm and dissection, and have a high risk of aortic dissection or rupture at an early age and at aortic diameters that ordinarily are not predictive of these events. Recently, LDS has been subdivided in LDS type I (LDSI) and type II (LDSII) on the basis of the presence or the absence of cranio-facial involvement, respectively. Furthermore, LDSII patients display at least two of the major signs of vascular Ehlers-Danlos syndrome. LDS is caused by mutations in the transforming growth factor (TGF) beta-receptor I (TGFBR1) and II (TGFBR2) genes. The aim of this study was the clinical and molecular characterization of two LDS patients

Arterial tortuosity syndrome in two Italian paediatric patients

<p>Abstract</p> <p>Background</p> <p>Arterial tortuosity syndrome (ATS) (OMIM #208050) is a rare autosomal recessive connective tissue disorder characterized by tortuosity and elongation of the large and medium-sized arteries, propensity to aneurysms formation, vascular dissection, and pulmonary arteries stenosis. ATS is caused by mutations in <it>SLC2A10 </it>gene, encoding for the facilitative glucose transporter 10 (GLUT10). So far, 17 <it>SLC2A10 </it>mutations have been reported in 32 families, two of which were Italian with a total of five patients. Here we present the clinical and molecular characterization of two novel Italian paediatric ATS patients.</p> <p>Methods</p> <p>The exons and intronic flanking regions of <it>SLC2A10 </it>gene were amplified and direct sequencing was performed.</p> <p>Results</p> <p>In both patients, the involvement of major- and medium-sized arteries was characteristic; the nonvascular connective tissue manifestations were mild and not pathognomic of the disorder. Both patients, born from non-consanguineous parents, were heterozygous for two different <it>SLC2A10 </it>mutations, three of which were recurrent and one was novel (p.Arg231Trp). This mutation is localized at the endofacial loop between the transmembrane domains 6 and 7 of GLUT10.</p> <p>Conclusion</p> <p>Two novel ATS patients were characterized at clinical and molecular level. Overall, four ATS unrelated families are known in Italy so far. Though ATS clinical delineation improved in the last years, further works in the comprehension of disease presentation and complications onset, particularly in paediatric age, and on ATS molecular basis are needed to add new insights for diagnosis and prevention strategies for related complications.</p

Colonoscopic findings in coeliac disease on a gluten-free diet

Background: to date, there are few data on colonoscopic findings in patients with celiac disease, and most of these obtained in patients with iron deficiency anaemia. Aims: we assessed colonoscopic findings in unselected pa tients with coeliac disease, since there are no studies available also considering morphological aspects, and there is literature sugges tion of increased prevalence of colorectal tumours. Material and methods: colonoscopies with multiple biopsies were retrospectively analyzed in 42 coeliac disease patients on gluten-free diet above age 40; 16 had clinical or laboratory fea tures of iron deficiency anaemia. Mucosal biopsies were evaluated for the presence of intraepithelial lymphocytes and of mucosal eosinophils, in addition to conventional histologic assessment, and compared with those obtained in 15 controls. Results: macroscopic abnormalities (polyps, diverticula, in flammatory changes) were found in 26% of patients. Microscopic abnormalities (lymphocytic colitis, melanosis coli, rectal histiocyto sis) were found in 36% of patients. None of these findings was found in controls. Coeliac disease patients had significantly higher eosinophil score than controls in the right colon, whereas this was not significantly different between groups in the left colon. Conclusions: colonoscopic findings in coeliac disease on gluten-free diet may reveal significant findings, even in patients without iron deficiency anaemia. There is the need of further stud ies in larger cohorts of patients to establish whether colonoscopy in these patients may be clinically useful